The field of this invention is mortarless retaining walls.
Mortarless concrete block retaining walls have the advantages that they are inexpensive, easy to construct with unskilled labor, have long life, and will adapt to ground subsidence which could crack a poured concrete or mortared wall.
Many mortarless retaining walls have been constructed, using a wide variety of materials. Conventional mortarless retaining walls used to hold earth embankments are typically made of poured concrete, blocks of stone and concrete, and railroad ties. To provide adequate strength and long life, a retaining wall preferably is tilted somewhat into the embankment. The tiers of concrete blocks are progressively set back from lower tiers. In Dean Jr., U.S. Pat. No. 4,920,712, tiers of concrete blocks are held in progressively set-back relation by a complex arrangement of metal clips which hook into apertures in the back walls of individual blocks. This is costly and making curved walls with these blocks and clips is difficult and requires considerable skill. For example, to make a wall with an outside curvature (that is, outwardly convex) certain ears that are required for a straight wall must be carefully and precisely knocked off.
In Forsberg, U.S. Pat. Nos. 4,825,619 and 4,914,876, tiers of concrete blocks are progressively set back by a complex arrangement of multiple through-holes, cavities, recesses and pockets in blocks which are interlocked by pins extending from holes in one tier of blocks into arcuate pockets in blocks of the next tier above or below. These arcuate pockets plus a special recess are in the top surface of each block but are not the bottom surface (and vice versa), so the top and bottom surfaces are different and not interchangeable. Care must be exercised to keep the proper side of the block up or down while assembling a wall. Further, there are severe limitations in the minimum wall curvatures possible with any one configuration of the arcuate pockets required in the individual blocks.
These and other disadvantages of conventional retaining walls are overcome by the special wall blocks and offset pins of the present invention which will now to be described.